As soon as the nib reaches its withdrawn rest position, a component of the cam operating device is coupled and withheld by a retaining member of a safety device arranged parallel to the cam operating device so as to maintain the nib in its withdrawn position.
Generally, prior art safety devices comprise a motorized rocker lever, which is generally arranged outside the nib, is provided with a coupling tooth and is pivoted to the frame to rotate with respect thereto between a coupling and retaining position, in which it withholds the component preventing any movement of the nib, and an decoupling or release position, in which it allows the component, and therefore also the nib, to translate towards its forward locking position.
Although prior art steering locks of the type described above are used universally, they are not completely adequate and reliable, as, after long operating times and above all following an accident, the certainty of the nib always being maintained in its withdrawn position and consequently of the shaft being free to rotate can only be achieved by strengthening the parts most susceptible to wear or most at risk of breaking and/or by using high strength materials, such as metals, and therefore with an inevitable increase in weight, overall dimensions and production costs.